Semiconductor device

ABSTRACT

There is provided a semiconductor device in which an initial resistance value can be kept even in the case where stress is applied by packaging or the like. A thin film resistor of the semiconductor device is composed of a P-type thin film resistor made from a P-type semiconductor thin film and an N-type thin film resistor made from an N-type semiconductor thin film. Thus, a variation in a resistance value in the case where the stress is applied is prevented. Also, in a bleeder resistance circuit, a resistance value as one unit is defined by a resistance value obtained by a lamination of the P-type thin film resistor and the N-type thin film resistor. Therefore, even if the stress is applied, variations in resistance values of respective resistors are cancelled and thus an accurate voltage dividing ratio can be kept. Further, an area of the bleeder resistance circuit can be reduced.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device, and moreparticularly to a semiconductor device having a thin film resistor; ableeder resistance circuit using a thin film resistor; and to asemiconductor device having the bleeder resistance circuit.

[0003] 2. Description of the Related Art

[0004] Conventionally, a resistor made from a semiconductor thin filmsuch as polysilicon and a bleeder resistance circuit using the resistorare used in many cases, and a resistor and a bleeder resistance circuit,which are formed using a semiconductor thin film having a conductivitytype of either an N-type or a P-type, have been known.

[0005] However, when stress is applied to the conventional thin filmresistor, for example, when resin packaging is made, there is a problemin that a resistance value of the thin film resistor is varied. Also, inthe case of the bleeder resistance circuit, there is a problem in that avoltage dividing ratio is often varied after the resin packaging.

SUMMARY OF THE INVENTION

[0006] The present invention has been made in view of the above, and anobject of the present invention is therefore to provide a bleederresistance circuit with high precision, in which an initial resistancevalue is kept after packaging and an accurate voltage dividing ratio canbe kept in the case of the bleeder resistance circuit, and asemiconductor device with high precision using such a bleeder resistancecircuit, for example, a semiconductor device such as a voltage detectoror a voltage regulator.

[0007] To achieve the above object, a means adopted in a semiconductordevice of the present invention is as follows. That is, a thin filmresistor and a thin film resistor of a bleeder resistance circuit usinga plurality of the thin film resistors are composed of a P-type thinfilm resistor made from a P-type semiconductor thin film and an N-typethin film resistor made from an N-type semiconductor thin film. Also, itis characterized in that a resistance value which is one unit in thebleeder resistance circuit is defined by a resistance value obtained bya combination of the P-type thin film resistor and the N-type thin filmresistor and thus variations in resistance values of the P-type thinfilm resistor and the N-type thin film resistor by a piezo effect, whichare described below, are cancelled each other. Further, it ischaracterized in that the P-type thin film resistor and the N-type thinfilm resistor are laminated in a vertical direction and thus anoccupying area of the bleeder resistance circuit is reduced.

[0008] Hereinafter, variations in resistance values by the piezo effectand an influence on the bleeder resistance circuit will be described.

[0009] When the stress is applied to the thin film resistor, theresistance value of the thin film resistor is varied by a so-calledpiezo effect, and the resistance value of the P-type thin film resistoris varied in the direction opposite to a variation in the resistancevalue of the N-type thin film resistor. This is also confirmed byexperiments of the present inventor(s). For example, the resistancevalue of the P-type thin film resistor is decreased and the resistancevalue of the N-type thin film resistor is increased. The direction ofthe variation is changed depending on the direction of the stress.

[0010] When the IC is packaged by a resin, the stress is produced. Thus,as described above, the resistance value of the thin film resistor isvaried by the piezo effect. Although the bleeder resistance circuit isused for obtaining an accurate voltage dividing ratio, since theresistance values of the respective resistors are varied, the voltagedividing ratio is also varied.

[0011] The thin film resistor according to the present invention iscomposed of the P-type thin film resistor made from the P-typesemiconductor thin film and the N-type thin film resistor made from theN-type semiconductor thin film. Thus, even if the stress is applied, avariation in the resistance value can be prevented. Also, a resistancevalue which is one unit in the bleeder resistance circuit is defined bya resistance value obtained by a combination of the P-type thin filmresistor and the N-type thin film resistor. Therefore, even if thestress is applied, variations in the resistance values of the respectiveresistors are cancelled and thus an accurate voltage dividing ratio canbe kept. Further, the P-type thin film resistor and the N-type thin filmresistor are laminated in a vertical direction, and thus an occupyingarea of the bleeder resistance circuit can be reduced.

[0012] The thin film resistor of the semiconductor device according tothe present invention is composed of the P-type thin film resistor madefrom the P-type semiconductor thin film and the N-type thin filmresistor made from the N-type semiconductor thin film. Therefore, evenif the stress is applied by resin packaging or the like, variations inthe resistance values of the respective resistors are cancelled and thusan initial resistance value can be kept. Also, a resistance value whichis one unit in the bleeder resistance circuit is defined by a resistancevalue obtained by a combination of the P-type thin film resistor and theN-type thin film resistor. Thus, an accurate voltage dividing ratio canbe kept. When such a bleeder resistance circuit is used, a semiconductordevice with high precision, for example, a semiconductor device such asa voltage detector or a voltage regulator can be obtained. Further, theP-type thin film resistor and the N-type thin film resistor arelaminated in a vertical direction, and thus an occupying area of thebleeder resistance circuit can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the accompanying drawings:

[0014]FIG. 1 is a schematic cross sectional view showing a semiconductorthin film resistor in a semiconductor device according to a firstembodiment of the present invention;

[0015]FIG. 2 is a schematic cross sectional view showing a semiconductorthin film resistor in a semiconductor device according to a secondembodiment of the present invention;

[0016]FIG. 3 is a block diagram of one embodiment of a voltage detectorusing a bleeder resistance circuit according to the present invention;and

[0017]FIG. 4 is a block diagram of one embodiment of a voltage regulatorusing a bleeder resistance circuit according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] Hereinafter, a preferred embodiment of the present invention willbe described with reference to the drawings.

[0019]FIG. 1 is a schematic cross sectional view showing a semiconductorthin film resistor in a semiconductor device according to a firstembodiment of the present invention.

[0020] A first insulating film 102 is formed on a semiconductorsubstrate 101. A P-type polysilicon resistor 703 and an N-typepolysilicon resistor 706 are formed on the first insulating film 102.The P-type polysilicon resistor 703 has a P-type high resistance region702 sandwiched between P-type low resistance regions 701 including heavyP-type impurities for making electrical connection with wirings 802. TheN-type polysilicon resistor 706 has an N-type high resistance region 705sandwiched between N-type low resistance regions 704 including heavyN-type impurities for making electrical connection with wirings 802. Thewirings 802 made of aluminum are connected with the P-type lowresistance regions 701 and the N-type low resistance regions 704. Here,even if stress is applied by resin packaging or the like, a variation ina resistance value of the P-type polysilicon resistor 703 and avariation in a resistance value of the N-type polysilicon resistor 706can be cancelled each other. Thus, a resistance value of a resistor 707obtained by a combination of the P-type polysilicon resistor 703 and theN-type polysilicon resistor 706 can be kept to an initial resistancevalue.

[0021] In FIG. 1, the example of a combination of one P-type polysiliconresistor 703 and one N-type polysilicon resistor 706 is shown. However,the resistor 707 may be formed by a combination of a plurality of theP-type polysilicon resistors 703 and a plurality of the N-typepolysilicon resistors 706.

[0022]FIG. 2 is a schematic cross sectional view showing a semiconductorthin film resistor in a semiconductor device according to a secondembodiment of the present invention.

[0023] The first insulating film 102 is formed on the semiconductorsubstrate 101. A P-type polysilicon resistor 703 having a P-type highresistance region 702 sandwiched between P-type low resistance regions701 including heavy P-type impurities for making electrical connectionwith wirings 802 is formed on the first insulating film 102. Further, anN-type polysilicon resistor 706 having an N-type high resistance region705 sandwiched between N-type low resistance regions 704 including heavyN-type impurities for making electrical connection with wirings 802 isformed on the P-type polysilicon resistor 703 through a secondinsulating film 801. Here, one of the P-type low resistance regions 701and one of the N-type low resistance regions 704 are connected with eachother through the wiring 802 made of aluminum in the same contact hole804. The wiring 802 made of aluminum is extended onto the N-typepolysilicon resistor 706. Since the P-type polysilicon resistor 703 andthe N-type polysilicon resistor 706 are laminated in a verticaldirection, an occupying area of the bleeder resistance circuit in an ICchip can be reduced.

[0024] In FIG. 2, the example of a lamination of one P-type polysiliconresistor 703 and one N-type polysilicon resistor 706 is shown. However,the resistor 707 may be formed by a lamination of a plurality of theP-type polysilicon resistors 703 and a plurality of the N-typepolysilicon resistors 706. Also, in the example shown in FIG. 2, theN-type polysilicon resistor 706 is formed on the P-type polysiliconresistor 703. However, the P-type polysilicon resistor 703 may be formedon the N-type polysilicon resistor 706.

[0025] The resistor 707 obtained by a combination of the P-typepolysilicon resistor 703 and the N-type polysilicon resistor 706, asshown in FIGS. 1 and 2, is defined as one unit of the bleeder resistancecircuit. Then, a plurality of resistors 707 is formed to construct theentire bleeder resistance circuit. In this manner, even if stress isapplied by resin packaging or the like, an accurate voltage dividingratio can be kept. When such a bleeder resistance circuit is used, asemiconductor device with high precision, for example, a semiconductordevice such as a voltage detector or a voltage regulator can beobtained.

[0026]FIG. 3 is a block diagram of one embodiment of a voltage detectorusing a bleeder resistance circuit according to the present invention.

[0027] For the purpose of simplification, an example of a simple circuitis shown. However, in the case of an actual product, the other functionsmay be added if necessary.

[0028] Basic circuit structure elements of the voltage detector are acurrent source 903, a reference voltage circuit 901, a bleederresistance circuit 902, and a differential amplifier 904. Further, aninverter 906, N-type transistors 905 and 908, a P-type transistor 907and the like are added. Hereinafter, a part of the operation will besimply described.

[0029] When a voltage VDD is a predetermined reset voltage or higher,the N-type transistors 905 and 908 are turned OFF and the P-typetransistor 907 is turned ON. Thus, the voltage VDD is output to theoutput terminal OUT.

[0030] At this point, the input voltage to the differential amplifier904 becomes (RB+RC)/(RA +RB+RC)×VDD.

[0031] When the voltage VDD decreases and becomes a detection voltage orlower, a voltage VSS is output to the output terminal OUT. At thispoint, the N-type transistor 905 is turned ON and the input voltage tothe differential amplifier 904 becomes RB/(RA+RB)×VDD.

[0032] As described above, the basic operation is performed such thatthe reference voltage generated in the reference voltage circuit 901 iscompared with the voltage divided by the bleeder resistance circuit 902in the differential amplifier 904. Thus, the precision of the voltagedivided by the bleeder resistance circuit 902 is very important. If thevoltage dividing precision of the bleeder resistance circuit 902 is low,the input voltage to the differential amplifier 904 is varied and thepredetermined reset voltage or the predetermined detection voltage isnot obtained. When the bleeder resistance circuit according to thepresent invention is used, the voltage dividing with high precisionafter an IC is packaged by resin is allowed. Thus, a yield of theproduct as the IC can be improved and the voltage detector with higherprecision can be manufactured.

[0033]FIG. 4 is a block diagram of one embodiment of a voltage regulatorusing the bleeder resistance circuit according to the present invention.

[0034] For the purpose of simplification, an example of a simple circuitis shown. However, in the case of an actual product, the other functionsmay be added if necessary.

[0035] Basic circuit structure elements of the voltage regulator are acurrent source 903, a reference voltage circuit 901, a bleederresistance circuit 902, a differential amplifier 904, a P-typetransistor 910 which acts as a current controlled transistor, and thelike. Hereinafter, a part of the operation will be simply described.

[0036] The differential amplifier 904 compares the voltage divided bythe bleeder resistance circuit 902 with the reference voltage generatedin the reference voltage circuit 901, and then supplies, to the P-typetransistor 910, a gate voltage required for obtaining a constant outputvoltage VOUT which is not influenced by changes in an input voltage VINand a temperature. In the voltage regulator, as in the case of thevoltage detector described in FIG. 3, the basic operation is performedsuch that the reference voltage generated in the reference voltagecircuit 901 is compared with the voltage divided by the bleederresistance circuit 902 in the differential amplifier 904. Thus, theprecision of the voltage divided by the bleeder resistance circuit 902is very important. If the voltage dividing precision of the bleederresistance circuit 902 is low, the input voltage to the differentialamplifier 904 is varied and the predetermined output voltage VOUT is notobtained. When the bleeder resistance circuit according to the presentinvention is used, the voltage dividing with high precision after an ICis packaged by resin is allowed. Thus, the yield of the product as theIC can be improved and the voltage regulator with higher precision canbe manufactured.

[0037] As described above, the thin film resistor of the semiconductordevice according to the present invention is composed of the P-type thinfilm resistor made from the P-type semiconductor thin film and theN-type thin film resistor made from the N-type semiconductor thin film.Therefore, even if stress is applied by resin packaging or the like,variations in resistance values of respective resistors are cancelledand thus an initial resistance value can be kept. Also, in the bleederresistance circuit, a resistance value as one unit is defined by aresistance value obtained by a combination of the P-type thin filmresistor and the N-type thin film resistor. Thus, an accurate voltagedividing ratio can be kept. Further, since the P-type thin film resistorand the N-type thin film resistor are laminated, an area of the bleederresistance circuit can be reduced. When such a bleeder resistancecircuit is used, there is an effect that a semiconductor device withhigh precision, for example, a semiconductor device such as a voltagedetector or a voltage regulator can be obtained with a small chip size.

What is claimed is:
 1. A semiconductor device having at least one thinfilm resistor, wherein the thin film resistor comprises a combination ofa P-type thin film resistor made from a P-type semiconductor thin filmand an N-type thin film resistor made from an N-type semiconductor thinfilm.
 2. A semiconductor device according to claim 1, having a bleederresistance circuit composed of a plurality of the thin film resistors,wherein a resistance value as one unit in the bleeder resistance circuitis defined by a resistance value obtained by the combination of theP-type thin film resistor and the N-type thin film resistor.
 3. Asemiconductor device according to claim 1, wherein a resistor definingthe resistance value as one unit in the bleeder resistance circuit isformed of a resistance constructed by a lamination of the P-type thinfilm resistor and the N-type thin film resistor in a vertical direction.4. A semiconductor device according to claim 1, wherein the thin filmresistor comprises polysilicon film.
 5. A semiconductor device accordingto claim 2, wherein the thin film resistor comprises polysilicon film.6. A semiconductor device according to claim 3, wherein the thin filmresistor comprises polysilicon film.